X-ray Spectrum Measurement Using Filter Wheel Pre-filters
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Solution Overview
Problem
Current x-ray CT systems using polychromatic sources face inefficiencies in spectrum measurement and calibration, leading to time-consuming procedures and potential errors due to changes in x-ray spectra over time, especially during long-running scans, which result in beam hardening artifacts and inaccuracies in tomographic reconstructions.
Innovation Solution
A simplified x-ray spectrum measurement and estimation system utilizing a filter wheel with pre-filters of different materials and thicknesses, allowing for baseline spectrum creation and real-time monitoring of x-ray source spectrum changes, enabling recalibration without the need for standard phantoms and reducing the number of required measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If standard phantom-based spectrum measurement procedures are used, then measurement accuracy is maintained, but measurement time increases significantly and errors occur during long-running scans
Solution Approach 1:
The patent extracts the spectrum measurement function from the standard phantom-based procedure by implementing real-time monitoring of x-ray source spectrum changes during scans. This allows the system to measure only necessary parameters continuously rather than performing complete phantom-based measurements, significantly reducing measurement time while maintaining accuracy.
Solution Approach 2:
The patent performs preliminary characterization of the x-ray source spectrum during system setup or calibration phases. This preliminary data is then used to detect and correct spectrum changes during operation without requiring full phantom-based remeasurement, reducing both time and potential errors during long-running scans.
2Power
If polychromatic x-ray beams are used, then source power is increased, but beam hardening artifacts occur in tomographic reconstructions
Solution Approach 1:
The patent implements real-time feedback monitoring of x-ray source spectrum changes during scans. By continuously measuring transmission values and detecting spectrum drift, the system can dynamically adjust reconstruction parameters or apply corrections to eliminate beam hardening artifacts while maintaining the high power benefits of polychromatic beams.
Solution Approach 2:
The patent changes the parameters used in tomographic reconstruction based on measured spectrum characteristics. By adapting reconstruction algorithms to the actual polychromatic spectrum measured during scanning, the system maintains image quality and reduces artifacts while utilizing the full power of polychromatic x-ray sources.
3Ease of operation
If x-ray source spectrum changes are not monitored, then system operation is simplified, but inaccuracies in tomographic reconstructions occur
Solution Approach 1:
The patent implements self-service spectrum monitoring where the system automatically detects and corrects its own spectrum changes without external intervention. The x-ray CT system continuously measures transmission values and performs self-calibration during operation, maintaining reconstruction accuracy while requiring minimal operator involvement.
4Measurement precision
If multiple measurements are performed for spectrum characterization, then measurement accuracy is improved, but measurement complexity and time increase
Solution Approach 1:
The patent performs partial spectrum characterization by measuring only the necessary transmission values required for accurate spectrum determination. Rather than performing complete multi-parameter measurements, the system measures a minimal sufficient set of transmission values through pre-filters, reducing procedural complexity while maintaining measurement accuracy.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly reduces the time and potential errors in spectrum measurement, allows for continuous monitoring and recalibration during scans, and minimizes beam hardening artifacts in tomographic reconstructions, enhancing the accuracy and efficiency of x-ray CT systems.
Implementation Method 1
The spectra are characterized by a continuous spectrum of bremsstrahlung ('braking radiation') x-rays
Implementation Method 2
secondary x-ray emissions at specific frequencies produced due to ionization and de-excitation of core electrons of the anode material, also known as x-ray fluorescence (XRF)
Implementation Method 3
The x-rays not absorbed or scattered away are then detected by a detector system
Data Source
Figure 1
Figure 2
Figure 3A~3B-1
AI summary
A spectrum measurement and estimation method for tomographic reconstruction, beam hardening correction, dual-energy CT and system diagnosis, etc., comprises determining the spectra for combinations of source acceleration voltage, pre-filters and/or detectors and after measuring the transmission values of several pre-filters, calculating corrected spectra for the combinations of the source acceleration voltage, pre-filters and/or detectors.